Investigation of challenges related to vapour explosion modelling in sodium

•Understanding and modelling of key vapour explosion processes in sodium is discussed.•Capability of MC3D code to simulate vapour explosions in sodium is supported.•Pressurization in sodium seems to be intrinsically limited to moderate pressures.•Vapour explosions in sodium might be simulated as an intensive premixing phase. The aim of the paper is to highlight the research priorities for the sodium vapour explosion modelling with the fuel-coolant interaction codes. Several simulations were performed with the MC3D code (IRSN, France) to support the qualitative and quantitative assessment of the modelling challenges. The main findings are: (1) the MC3D code is capable to cover vapour explosions in sodium, (2) the need for super-critical sodium tables is indicated, (3) the vapour explosion in sodium might be considered as an intensive premixing phase, (4) the experimentally observed limitation of the pressure to some MPa is also observed with simulations, (5) in future the thermal fine fragmentation modelling might be needed and (6) an experimental study of the heat transfer around the fine fragments shall be performed.